Page History

...

In this example, the call to the security-critical function is not executed. It is possible that a reviewer examining this page may could incorrectly assume that the code is executed.

...

Instead of using /* and */ to comment out blocks of code, comment out blocks of code using conditional compilation (e.g.for example, #if, #ifdef, or #ifndef).

#if 0  /* use of critical security function no
        * longer necessary */
security_critical_function();
/* some other comment */
#endif

...

The NOTREACHED comment tells some compilers and static analysis tools not to complain about this unreachable code.   It also serves as documentation. 

if (0) {  /* use of critical security function no
           * longer necessary, for now */
  /*NOTREACHED*/
  security_critical_function();
  /* some other comment */
}

This is an instance of exception MSC07-EX2 to guideline recommendation MSC07-C. Detect and remove dead code.

...

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Related Guidelines

CERT C++ Secure Coding Standard: MSC04-CPP. Use comments consistently and in a readable fashion

Bibliography

Wiki Markup\[[ISO/IEC 9899:1999|AA. Bibliography#ISO/IEC 9899-1999]\] Section 6.4.9, "Comments," and Section 6.10.1, "Conditional inclusion"

MISRA Rule \[[MISRA 04|AA. Bibliography#MISRA 04]\] Rule 2.2, "Source code shall only use /\* ... \ */ style comments," Rule 2.3, "The character sequence /\* shall not be used within a comment," and Rule 2.4, "Sections of code should not be "commented out"

Bibliography

\[[Summit 052005|AA. Bibliography#Summit 05]\] [Question 11.19|http://c-faq.com/ansi/ifdefsyntax.html]

...